278 PROFESSOR C. R. MARSHALL ON 



When the respiration is paralysed and does not recover spontaneously the blood- 

 pressure after a brief interval falls rapidly to a few millimetres. That this fall is 

 mainly asphyxial is proved by artificial respiration, which quickly raises the pressure 

 to the level it would probably have reached if respiration had recommenced. If the 

 substance is injected after the administration of pilocarpine or during stimulation of the 

 vagus a rise of blood-pressure always occurs. 



The fall in blood-pressure is probably cardiac in origin, since it is accompanied 

 by a diminution in the frequency of the heart-beats ; and as the vagus nerve endings 

 are paralysed, the action of the drug would seem to be on the muscular tissue of the 

 heart itself. The rise of blood-pressure seen occasionally in experiments with cats 

 is accompanied by an increase in the number of the heart-beats due to paralysis of 

 the vagal terminations. The cardiac muscle in these cases is not depressed sufficiently 

 to counteract the effect of paralysing the vagus, but that some depression is produced 

 is shown by the rise of blood-pressure being less than that obtained with a correspond- 

 ing physiological dose of atropine. Moreover, increase in dose leads to a somewhat 

 smaller rise of pressure. Why this prolonged rise should occur in isolated cases is difficult 

 to explain. Probably a certain concentration of the drug in the heart acting for a brief 

 interval only is necessary, but the condition of the heart itself may also be a factor. 



Action on Voluntary Muscle and Motor Nerves. 



The activity both of motor nerves, or more probably their terminations, and of 

 voluntary muscle, is depressed by this drug. In rabbits the nerve endings appear to 

 be more susceptible than the muscle ; in frogs the muscle is at least as powerfully 

 affected as the nerves. After an injection of 0'24 mg. protocatechyl-tropeine 

 hydrochloride per gramme body-weight into the dorsal lymph sac of a frog, muscular 

 weakness appeared within five minutes — the head began to droop and the animal 

 became unable to turn over when placed on the back. A few minutes later the frog 

 was quite flaccid. This condition and the paralysis of the respiration referred to 

 previously was maintained during the period of observation (the frog died during the 

 night). Although apparently completely paralysed, the frog occasionally made a slight 

 voluntary movement, and a slight reflex was several times obtained on pinching a toe 

 moderately strongly for some seconds. After 0*16 mg. per gramme body- weight was 

 injected similar symptoms were observed. The head commenced to droop in twenty 

 minutes and the animal gradually sank on the table. The reflexes, however, remained 

 distinct, and when placed on the back an hour after the injection the frog recovered 

 once, but not twice, from this position. The frog was pithed seventy-two minutes after 

 the injection and the irritability of the sciatic nerves and gastrocnemii muscles tested. 

 The sciatics reacted with the secondary coil at 35 cm., the muscles with the coil at 28 

 cm. The injection of # 08 mg. per gramme body-weight produced only slight muscular 

 depression. 



